Mg Of Urea Research Articles

Nitrogen: from discovery, plant assimilation, sustainable usage to current enhanced efficiency fertilizers technologies – A review

ABSTRACT From 1913 onwards, the global situation changed from a scenario of nitrogen (N) scarcity to an abundance of ammonia (NH 3 ) produced synthetically via the Haber-Bosch process. Several N compounds have been synthesized since then, with urea becoming the main source of N, accounting for 55 % of current N consumption. However, N efficiency in agroecosystems is low and, normally, N recovery in cultivated plants is less than 50 %. This occurs because a large amount of reactive N is lost to the environment, inducing various forms of pollution, threatening human and environmental health, in addition to causing a negative economic impact on the farmer. The main processes responsible for low N efficiency are NH 3 volatilization, leaching, and N denitrification. Considering global NH 3 volatilization losses of 14 %, it can be assumed that up to 8.6 million Mg of urea are lost every year in the form of NH 3 . For each ton of NH 3 produced, 1.9 to 3.8 Mg of CO 2 is emitted into the atmosphere. Therefore, increasing N use efficiency (NUE) without compromising yield is a necessity and a challenge for crop improvement programs and current management systems, in addition to reducing greenhouse gas emissions. In this context, enhanced efficiency fertilizers (EEFs), which contain technologies that minimize the potential for nutrient losses compared to conventional sources, are an alternative to increasing the efficiency of nitrogen fertilization. Currently, EEFs are classified into three categories: stabilized, slow-release, and controlled-release. This study aims to understand the technologies used to produce EEFs and the factors that govern their availability to plants. This review covers the following topics: the discovery of N, N dynamics in the soil-atmosphere system, N assimilation in plants, strategies to increase NUE in agrosystems, NH 3 synthesis, NH 3 volatilization losses, N fertilizer technologies, the importance of characterization of EEFs, conventional nitrate or ammonium-based fertilizers to reduce gaseous losses of NH 3 and future prospects for the use of N fertilizers in agriculture.

Plant growth promotion of radish by rhizosphere dwelling bacteria

The present study was carried out with the aim to develop a plant growth-promoting rhizobacterial inoculant for improving the growth of radish. A total of 20 rhizobacteria were isolated and then tested for multifarious plant growth-promoting traits. The isolates exhibited tricalcium phosphate and zinc solubilization, production of siderophores, auxins, ammonia and growth on different nitrogen free medium. Out of 20 isolates, two potential bacterial isolates (RM3 and RL3) were selected on the basis of PGP traits for evaluation of their potential to promote growth of radish under pot conditions. In green house experiment, these isolates when used as consortium showed a significant improvement in soil enzymatic activities (viz. dehydrogenase: 12.99 µg TPF formed h-1 g of soil-1, alkaline phosphatase: 11.94 µg PNP formed h-1 g of soil-1 and urease: 401.65 µg urea hydrolyzed formed h-1g of soil-1) and plant growth parameters (shoot length: 38.76 cm, leaf area: 267cm2, fresh leaf weight:106.05 g, dry leaf weight:1.23 g, number of leaves per plant: 23, fresh root weight:111.69 g, dry root weight: 2.06 g, root length: 34.04 cm and root diameter: 3.33 cm) relative to control as well as other bioinoculants. These bacteria were tentatively identified as Bacillus (RM3) and Pseudomonas (RL3) on the basis of biochemical tests.

Confining SnS2 Ultrathin Nanosheets in Hollow Carbon Nanostructures for Efficient Capacitive Sodium Storage

Summary Tin disulfide (SnS 2 ) is a promising anode material for sodium-ion batteries because of its high specific capacity. However, the low conductivity and large volume change during reaction with Na + ions greatly limit its practical application. Herein, a multistep templating method has been exploited for the rational design and synthesis of SnS 2 nanosheets confined in carbon nanotubes (SnS 2 @CNTs). To demonstrate the universality of this method, SnS 2 nanosheets confined in carbon nanoboxes (SnS 2 @CNBs) and hollow carbon nanospheres (SnS 2 @CNSs) have also been synthesized by simply changing the template in the reaction system. Due to their unique structural merits, the SnS 2 @CNTs, SnS 2 @CNBs, and SnS 2 @CNSs show improved sodium storage performance in terms of high specific capacity, good cycling stability, and superior rate capability.

Influence of synthesis parameters on particle properties and catalytic activity of rice roll-like Au/SiO2 nanocatalysts prepared in inverse miniemulsions

In our previous paper, we reported the synthesis of easily recyclable and highly active rice roll-like (RR-like) Au/SiO2 nanocatalysts (NCs) in inverse miniemulsions [Colloids Surf. A 517, 2017, 52–62]. In the present contribution, the influences of three key synthesis parameters, including the 3-aminopropyltriethoxysilane (APTES) content, reaction temperature, and urea amount, on the particle properties of the Au/SiO2 NCs were systematically investigated. The role of these synthesis parameters in the formation of SiO2 nanosupports and Au nanoparticles (NPs) was discovered. The RR-like SiO2 nanosupports could only be formed in the systems within the range of 20–80mol% of APTES content, at reaction temperatures above 60°C, and with more than 0.72mg of urea. The AuCl4− ions could be immobilized onto the aminopropyl-functionalized SiO2 nanosupports through a coordination interaction. The immobilized ions were reduced by the aminopropyl groups at elevated temperatures. The APTES content and reaction temperature play an important role in controlling the particle size and its distribution of Au NPs. The catalytic activity of Au/SiO2 NCs depends significantly on the APTES content. The RR-like Au/SiO2 NCs with smaller immobilized Au NPs and higher specific surface area display higher catalytic activity towards hydrogenation of p-nitrophenol.

The Birth and Development of Continuous Ambulatory Peritoneal Dialysis.

Peritoneal dialysis has a long and tortuous history. First done in animals in the late 1800s, it became clinically practical in the early 1960s. Peritoneal access was first achieved by intermittent abdominal puncture, and then through the development of a 'permanent access' when Silastic became available. The early design is appropriately named for Dr. Henry Tenckhoff. Successful peritoneal dialysis was performed intermittently with infusion of 2 liters of balanced fluid followed by a dwell time of 30-45 min, which in turn was followed by drainage and new infusion. The procedure was used almost exclusively in the intensive care setting but failed to achieve success when applied on a long-term basis. The new concept of extending the dwell time of the dialysis fluid to allow equilibration between an acceptable blood level of urea and the level of urea in the dialysis fluid remarkably reduced the fluid volume required to control uremic toxins and symptoms. This change also allowed the patient to be disconnected from all devices and freely move about as dialysis took place. It was concluded that an acceptable blood level of urea nitrogen was 70 mg %. Equilibration with dialysis fluid, five 2-liter exchanges for 10 liters per day, would allow the removal of 7,000 mg of urea, the average quantity generated on a diet of a 70-kg person eating 1 g of protein per kg of body weight per day. The procedure was originally called 'equilibrium peritoneal dialysis', but was later changed to 'continuous ambulatory peritoneal dialysis'.

Effect of organic and inorganic sources of nutrients on soil microbial activity and soil organic carbon build-up under rice in west coast of India

ABSTRACTThe effect of medium-term (5 years) application of organic and inorganic sources of nutrients (as mineral or inorganic fertilizers) on soil organic carbon (SOC), SOC stock, carbon (C) build-up rate, microbial and enzyme activities in flooded rice soils was tested in west coast of India. Compared to the application of vermicompost, glyricidia (Glyricidia maculate) (fresh) and eupatorium (Chromolaena adenophorum) (fresh) and dhaincha (Sesbania rostrata) (fresh), the application of farmyard manure (FYM) and combined application of paddy straw (dry) and water hyacinth (PsWh) (fresh) improved the SOC content significantly (p < 0.05). The lowest (p < 0.05) SOC content (0.81%) was observed in untreated control. The highest (p < 0.05) SOC stock (23.7 Mg C ha−1) was observed in FYM-treated plots followed by recommended dose of mineral fertilizer (RDF) (23.2 Mg C ha−1) and it was lowest (16.5 Mg C ha−1) in untreated control. Soil microbial biomass carbon (Cmb) (246 µg g−1 soil) and Cmb/SOC (1.92%) were highest (p < 0.05) in FYM-treated plot. The highest (p < 0.05) value of metabolic quotient (qCO2) was recorded under RDF (19.7 µg CO2-C g−1 Cmb h−1) and untreated control (19.6 µg CO2-C g−1 Cmb h−1). Application of organic and inorganic sources of nutrients impacted soil enzyme activities significantly (p < 0.05) with FYM causing highest dehydrogenase (20.5 µg TPF g−1 day−1), phosphatase (659 µg PNP g−1 h−1) and urease (0.29 µg urea g−1 h−1) activities. Application of organic source of nutrients especially FYM improved the microbial and enzyme activities in flooded and transplanted rice soils. Although the grain yield was higher with the application of RDF, but the use of FYM as an organic agricultural practice is more useful when efforts are intended to conserve more SOC and improved microbial activity.

Effects of microbial inoculations on soil chemical, biochemical and microbial biomass carbon of cassava (Manihot esculenta Crantz) growing Vertisols

Cassava is an important subsidiary food in the tropics. In Tamil Nadu, India, microbial cultures were used to eradicate the tuberous root rot of cassava. Hence, an experiment was conducted for two consecutive years to test the effects of coinoculation of microbes on soil properties. The surface soil from the experimental site was analysed for soil available nutrients, soil enzyme activities and microbial biomass carbon. The treatment of Azospirillum with Trichoderma at the 50% recommended N:P2O5:K2O (NPK) rate (50:25:50 kg ha−1) significantly increased soil available nitrogen (142.81 kg ha−1) by 72.66% over uninoculated control. There was a significant increase in available phosphorus in soil by the inoculation of AM (arbuscular mycorrhizal) fungi with Trichoderma at the 50% recommended NPK rate (41.04 kg ha−1) compared to other treatments. The application of Pseudomonas fluorescens with Trichoderma at the 50% recommended NPK rate significantly increased available iron (19.34 µg g−1) in soil. The treatment of Azospirillum with Trichoderma increased urease enzyme activity at the recommended NPK rate (816.32 μg urea hydrolyzed g−1 soil h−1). Soil application of all cultures at the 50% recommended NPK rate significantly increased dehydrogenase activity (88.63 μg TPF g−1 soil) and β-glucosidase activity (48.82 μg PNP g−1 soil) in soil. Inoculation of Trichoderma alone at the 50% recommended NPK rate significantly increased microbial biomass carbon (3748.85 μg g−1 soil). Thus, the microbial inoculations significantly increased soil available nutrient contents, enzyme activities such as urease, dehydrogenase and β-glucosidase activity and microbial biomass carbon by reducing the amount of the required fertilizer.

Performance study of a ‘constant phase angle based’ impedance sensor to detect milk adulteration

In this paper, a new type of impedance sensor is proposed to detect milk adulteration. The measurement is based on the change in constant value of the phase angle of the impedance sensor due to the change of ionic property of the adulterated milk. The performance of the sensor is tested for three different types of adulterated milk (milk adulterated with tap-water, urea and liquid-whey). It has been observed that the sensor can identify 5% of liquid-whey adulteration, 10% tap-water adulteration, and 0.6 mg of urea per ml of milk. The sensor is also tested to distinguish between synthetic milk and original milk and the result shows that it can differentiate these two when the synthetic milk is reconstructed by adding minimum15% of adulteration.

Milk urea concentration as an indicator of ammonia emission from dairy cow barn under restricted grazing

Bulk milk urea concentration was evaluated to assess its potential as an indicator of ammonia emission from a dairy cow barn in a situation with restricted grazing. An experiment was carried out with a herd of, on average, 52 Holstein-Friesian dairy cows. The cows were housed in a naturally ventilated barn with cubicles and a slatted floor, were fed ensiled forages and feed supplements, and each day were allowed 8.5h of grazing. The experiment was a balanced randomized block design, replicated 3 times. The experimental factor was the bulk milk urea level, which was adjusted to levels of 15, 35, and 55mg of urea per 100g of milk, respectively, by changing the level of nitrogen fertilization of the pasture, the herbage mass and grass regrowth age, and the level and type of feed supplement. Ammonia emission from the barn was measured using sulfur hexafluoride as the tracer gas. Ammonia emission generally increased upon an increase in adjusted milk urea levels. A dynamic regression model was used to predict ammonia emission from bulk milk urea concentration, temperature, and a slurry mixing index. This model accounted for 66% of the total variance in ammonia emission and showed that emission increases exponentially with increasing milk urea concentration. At levels of 20 and 30mg of urea per 100g of milk, ammonia emission increased by about 2.5 and 3.5%, respectively, when milk urea concentration increased by 1mg/100g. Furthermore, emissions from the barn increased 2.6% when temperature increased by 1°C. The study showed that bulk milk urea concentration is a useful indicator for ammonia emissions from a dairy cow barn in a situation with restricted grazing.

UREA LEVEL IN COWS’ MILK FED ON TOTAL MIXED RATION (TMR) AND TRADITIONAL SYSTEM IN SUMMER AND WINTER SEASON

In the research urea content in milk and frequency of the occurrence of samples with different urea level in milk of cows fed on total mixed ration (TMR) and traditional system in summer and winter season were analyzed. Analysis covered 14272 of milk samples. On account of urea level they were divided on three groups: to 140, 141-250 and above 250 mg of urea in 1 liter of milk. It was found that average urea content in milk of cows fed on total mixed rations (TMR) amounted to 196 mg.l-1. Milk of cows from farm applying traditional feeding system included 184 mg.l-1 of that constituent average. Both these values therefore could have been recognized as optimal. Urea level pointed out to the energy-protein unbalancing of feed rations in 55.6% (TMR) and 57.7% (traditional) of milk samples. Urea level in milk of cows fed in traditional system was at p≤0.01 higher (196 mg.l-1) in summer than in winter season (166 mg.l-1). In winter feeding season the frequency of the occurrence of milk samples indicating the lack of protein in feed rations (to 140 mg of urea in 1 liter) was 11.9% higher than in summer season.

Effect of organics on nitrogen transformations in soil under different moisture regimes

Awareness of the environmental aspects of the quality of crop production has increased in recent decades, leading to renewed interest in organics such as crop residues, green manures and organic manures. The effect of organics on urea transformation was investigated by conducting a laboratory incubation experiment in alluvial clay loam soil (Typic Ustifluvents) at 33±1°C with two moisture levels (1:1 soil:water ratio and field capacity). The rate of urea hydrolysis decreased as the time of incubation increased and the disappearance of urea N was associated with a corresponding increase in the (NH 4+ + NO 3− )-N content in soils treated with crop residues (rice straw and wheat straw), organic manures (poultry manure and farmyard manure) and green manures (cowpea and sesbania). In untreated soil, the time taken for the complete hydrolysis of the applied urea (200 μg urea N g −1 soil) was more than 96 h at both the moisture levels, whereas in amended soils it was completed in 48 h. The rate of urea hydrolysis was more rapid at field capacity than at the 1:1 soil:water ratio. Urea hydrolysis was higher in sesbaniatreated soils, followed by cowpea, poultry manure, farmyard manure, rice straw and wheat straw at both the moisture levels. At field capacity, 85.5% urea was hydrolysed in sesbania-treated soil as compared to 32% in untreated soil after 24 hours of incubation, while at the 1:1 soil:water ratio the corresponding values were 81.5 and 27.5%. Urea hydrolysis followed first order reaction kinetics at both the moisture levels.

Influence of Crop Residues and Organic Manures on the Hydrolysis of Urea in a Typic Haplustept

The emphasis on integrated use of organic amendments and fertilizers has made it imperative to study the effect of crop residues and organic manures on urea hydrolysis, which governs the release of N from urea fertilizer. Urea hydrolysis in soils is an enzymatic decomposition process facilitated by the extracellular enzyme urease. Our aim was to assess the influence of crop residues (rice straw, wheat straw) and organic manures (poultry manure, farm yard manure, cowpea, and sesbania) on urea hydrolysis by conducting a laboratory incubation experiment employing a Hasanpur silt loam soil (coarse loamy, mixed, hypothermic Typic Haplustept). The study was conducted at a constant temperature of 33 ± 1°C at two moisture levels (1:1 soil:water ratio and field capacity). The results showed that the rate of urea hydrolysis decreased with an increase in time of incubation (12 to 96 h), while the disappearance of urea N was associated with the corresponding increase in ( + )-N content in soils treated with crop residues and organic manures. In the nonamended soil, the time required for the complete hydrolysis of the applied urea (200 μg urea N g−1 soil) was more than 96 h at both the moisture levels, whereas in amended soils, 60 to 72 h of incubation periods were required for urea hydrolysis. The rate of urea hydrolysis in the amended soil was of the following order: sesbania > cowpea > poultry manure > farmyard manure > rice straw and wheat straw, irrespective of the moisture regime. Urea hydrolysis followed first-order kinetics in all the treatments at both moisture levels. The rate constant value for urease activity was higher at field capacity, indicating that urea hydrolysis proceeded rapidly under the condition of field capacity rather than saturated conditions (1:1 soil:water ratio).

Effect of Organic and Inorganic Nutrients for Soil Quality Conservation and Yield of Rainfed Low Land Rice in Sub‐tropical Plateau Region

AbstractThe effect of organic sources of nutrients and inorganic fertilizers, was studied on grain yield of lowland rice and some aspect of soil quality parameters in a field experiment at Agricultural Experimental Farm of Indian Statistical Institute, Giridih, situated at eastern plateau region of India, during consecutive years 1997–2002. Chemical fertilizers and various organic matters were applied to two rice cultivars, Sabita and Subarna. The highest mean grain yield was 3.53 t ha−1 and maximum agronomic efficiency was 60.3 % with the application of inorganic fertilizer followed by cow dung, where 3.47 t ha−1 grain yield was recorded with an agronomic efficiency of 57.5 %. Grain yield of rice recorded under organic sources of nutrients was not significantly different from that of inorganic fertilization though there was improvement in soil quality parameters under organic sources. Soil organic carbon (0.72 %), microbial biomass‐C (279.23 μg g−1 dry soil), urease activity with buffer (33.54 μg urea hydrolyzed g−1 oven‐dry soil) and non‐buffer (21.97 μg urea hydrolyzed g−1 of oven‐dry soil) methods and acid phosphatase activity (2.24 μg para‐nitrophenol released g−1 of oven‐dry soil) analysed following the harvest of the crop were highest under cow dung manure treatment; the most efficient organic source under the experiment. Mean grain yield of rice was significantly higher in Sabita cultivar over Subarna. The regression analyses among the variables have shown that there was linear relationship among soil parameters and grain yield of rice.

Long‐term follow‐up of 13C‐urea breath test results after Helicobacter pylori eradication: frequency and significance of borderline δ13CO2 values

The precise choice of cut-off point for the 13C-urea breath test to define whether it is positive or negative represents a controversial issue. To quantify the 13C-urea breath test result for several years following Helicobacter pylori eradication, and to evaluate the frequency and the significance of borderline delta13CO2 values. Two-hundred H. pylori eradicated patients confirmed by 13C-urea breath test (100 mg of urea, citric acid), and having had repeated this test yearly up to 5 years, were studied. Delta13CO2 values between 2 and 5/1000 were considered as borderline results. Eight H. pylori recurrences were observed during 406 patient-years of follow-up (1.97% yearly). In two of eight reinfected patients, the reinfection was preceded by a negative delta13CO2 value >2/1000. Borderline delta13CO2 values were detected in 4% of the 606 urea breath tests performed, and in 25% when only patients in whom H. pylori recurrence was detected in subsequent urea breath tests were included (P < 0.05). The negative-predictive value of a post-treatment delta13CO2 >2/1000 for the diagnosis of H. pylori recurrence was 99%. Positive and negative urea breath test results tend to cluster outside the range between 2/1000 and 5/1000. Nevertheless, a borderline urea breath test delta value (e.g. very close to the selected cut-off point) should be interpreted cautiously, and the result should probably be confirmed either by repeating the urea breath test or by other diagnostic methods. On the contrary, a delta13CO2 value <2/1000 very confidently confirms H. pylori eradication.

Absorption of urea through the oral mucosa and estimation of the percentage of secreted whole saliva inadvertently swallowed during saliva collection

To determine whether some of the urea added to certain chewing gums may be absorbed through the oral mucosa and whether some saliva is inadvertently swallowed during the collection of saliva elicited by the chewing of gum. On two occasions, 10 experienced saliva collectors made a 5 min collection of unstimulated whole saliva and then chewed gum for 10 min and during this time collected their saliva. On one occasion, they chewed one tablet of gum containing 0.5 mg of Phenol Red, a non-absorbable substance, and one tablet of a gum containing 27.3 mg of urea. On another occasion, they chewed two tablets of the Phenol Red gum. Their saliva and the chewed gum were assayed for their Phenol Red and urea contents and the totals calculated. Since saliva normally contains urea, the recovery of urea was calculated as the difference between the amounts recovered in the two collection sessions. The mean recovery of Phenol Red was 96.7%, but in three participants the amount recovered was less than the 95% confidence limits for assay error. The mean recovery of urea was 85.7% and in nine of the 10 participants, the amount recovered was less than the confidence limits for assay error. In all participants, the percentage urea recovery was less than that of Phenol Red. The results showed: (1) that Phenol Red appears to be a useful, non-absorbed marker for studies of drug absorption through the oral mucosa, (2) that when the salivary urea concentration is higher than that in plasma, urea may be absorbed through the oral mucosa, (3) that even experienced saliva collectors may inadvertently swallow some of the saliva they produce. This latter finding has implications for all clinical studies of saliva.

Review article: 13C‐urea breath test in the diagnosis of Helicobacter pylori infection – a critical review

The urea breath test is a non-invasive, simple and safe test which provides excellent accuracy both for the initial diagnosis of Helicobacter pylori infection and for the confirmation of its eradication after treatment. Some studies have found no differences between urea breath test performed under non-fasting conditions. The simplicity, good tolerance and economy of the citric acid test meal probably make its systematic use advisable. The urea breath test protocol may be performed with relatively low doses (<100 mg) of urea: 75 mg or even 50 mg seem to be sufficient. With the most widely used protocol (with citric acid and 75 mg of urea), excellent accuracy is obtained when breath samples are collected as early as 10-15 min after urea ingestion. A unique and generally proposed cut-off level is not possible because it has to be adapted to different factors, such as the test meal, the dose and type of urea, or the pre-/post-treatment setting. Fortunately, because positive and negative urea breath test results tend to cluster outside of the range between 2 and 5 per thousand, a change in cut-off value within this range would be expected to have little effect on clinical accuracy of the test.

In vitro evaluation of cross-circulation system using semipermeable membrane combined with whole liver perfusion

Introduction Many types of isolated hepatocytes-based bioartificial liver have been developed. However, to maintain hepatocyte-specific functions for a long period is still a significant challenge. The possibilities of rejection or viral transmission still remain as untackled obstacles. We developed a cross-circulation system, using a semipermeable membrane combined with whole liver perfusion. Detoxifying functions of the extracorporeal porcine liver and molecular movements across the membrane were evaluated in vitro. Methods The hollow-fiber module has a molecular cutoff of 100 kD. A spiked solution containing 500 mL low molecular dextran solution spiked with 12 mg ammonium chloride, 500 mg D-galactose, and 300 mg lidocaine, which mimicked a patient, was recirculated through the inner fiber space. The extracorporeal liver perfusion circuit consisted of an extra-fiber spaces. A reservoir containing 1000 mL healthy pig plasma, a membrane oxygenator, and a porcine whole liver. Both circuits circulated in the opposite direction for 6 hours. Result In 6 hours, 47.3% ± 10.2% of ammonia, 89.5% ± 1.7% of D-galactose, and 95.5% ± 1.0% of lidocaine were eliminated from the circuits; 66.5 ± 11.1 mg of urea were produced at the same time. Oxygen consumption was maintained between 0.248 and 0.259 mL/100 g liver/min for 6 hours. Movement of IgM was completely blocked by the 100-kD membrane, whereas albumin was freely transferred from the reservoir to the intrafiber space. Conclusion The perfusion experiments showed the possibility of using a whole liver with oxygenated plasma perfusion in a bioartificial liver system in vitro.

Perdas de nitrogênio por volatilização da amônia em três solos argilosos tratados com uréia

The soil nitrogen (N) losses in gaseous form depend on their intrinsic characteristics and also on the environmental conditions. In soils with the same texture class, the mineralogy of the clay size fraction and the amount of organic matter are the main factors that may affect the N dynamics. In the State of Paraná northerner region, variations in these characteristics are found in the toposequence of soils derived from basalts where, in the landscape upper part, highly weathered soils, such as the Latosols, are found and, in the other sections, younger soils, such as Neosols and eventually Vertisols, are found. The aim of the present work was to evaluate the N volatilization losses from ammonia, using three clayey soils (Red Dystroferric Latosol-LVdf, Litholic Neosol-RL and Ortic Hydromorphic Vertisol-VGo) submitted to two soil moisture contents (S8 and SS) and treated with urea. The ammonia volatilization of the applied urea was evaluated in 2000cm3 plastic recipients that received 500g of soil and 200mg of urea, for an accumulative period of 10 days. Paper filter collectors, previously humidified with H2SO4 measured the N-NH3 losses, which were placed 5cm above the soil surface. The results showed that the soils presented differences in the ammonia losses, related to the initial soil moisture contents and the mineralogy of the clay size fraction. In the lower moisture treatment (S8) the least weathered soils (RL and VGo) showed the lowest ammonia losses, due to the higher percentages of 2:1 clay type minerals. In the soil-saturated treatment the N-NH3 losses were not statistically significant among the soils

Effect of nitrogen intake on nitrogen recycling and urea transporter abundance in lambs.

Urea recycling in ruminants has been studied extensively in the past, but the mechanisms regulating the amount of urea recycled or excreted remain obscure. To elucidate the role of urea transporters (UT) in N recycling, nine Dorset-Finn ewe lambs (20.8 +/- 0.8 kg) were fed diets containing 15.5, 28.4, and 41.3 g of N/kg of DM for 25 d. Nitrogen balance and urea N kinetics were measured during the last 3 d of the period. Animals were then slaughtered and mucosa samples from the rumen, duodenum, ileum, and cecum, as well as kidney medulla and liver, were collected. Increasing N intake tended to increase N balance quadratically (1.5, 5.1, and 4.4 +/- 0.86 g of N/d, P < 0.09), and linearly increased urinary N excretion (2.4, 10, and 16.5 +/- 0.86 g N/d, P < 0.001) and plasma urea N concentration (4.3, 20.3, and 28.4 +/- 2.62 mg of urea N/dL, P < 0.001), but did not affect fecal N excretion (5.0 +/- 0.5 g of N/d; P < 0.94). Urea N production (2.4, 11.8, and 19.2 +/- 0.83 g of N/d; P < 0.001) and urinary urea N excretion (0.7, 7.0, and 13.4 +/- 0.73 g N/d; P < 0.001) increased linearly with N intake, as well as with the urea N recycled to the gastrointestinal tract (1.8, 4.8, and 5.8 +/- 0.40 g of N/d, P < 0.001). No changes due to N intake were observed for creatinine excretion (518 +/- 82.4 mg/d; P < 0.69) and clearance (46 +/- 10.7 mL/min; P < 0.56), but urea N clearance increased linearly with N intake (14.9, 24.4, and 34.9 +/- 5.9 mL/min; P < 0.04). Urea N reabsorption by the kidney tended to decrease (66.3, 38.5, 29.1 +/- 12.6%; P < 0.06) with increasing N content of the diet. Increasing the level of N intake increased linearly the weight of the liver as a proportion of BW (1.73, 1.88, and 2.22 +/- 0.15%, P < 0.03) but only tended to increase the weight of the kidneys (0.36, 0.37, and 0.50 +/- 0.05%, P < 0.08). Urea transporter B was present in all the tissues analyzed, but UT-A was detected only in kidney medulla, liver, and duodenum. Among animals on the three diets, no differences (P > 0.10) in UT abundance, quantified by densitometry, were found. Ruminal-wall urease activity decreased linearly (P < 0.02) with increasing level of N intake. Urease activity in duodenal, ileal, and cecal mucosa did not differ from zero (P > 0.10) in lambs on the high-protein diet. In the present experiment, urea transporter abundance in the kidney medulla and the gastrointestinal tract did not reflect the increase in urea-N reabsorption by the kidney and transferred into the gut.

Effect of nitrogen intake on nitrogen recycling and urea transporter abundance in lambs12

Urea recycling in ruminants has been studied extensively in the past, but the mechanisms regulating the amount of urea recycled or excreted remain obscure. To elucidate the role of urea transporters (UT) in N recycling, nine Dorset-Finn ewe lambs (20.8 ± 0.8 kg) were fed diets containing 15.5, 28.4, and 41.3 g of N/kg of DM for 25 d. Nitrogen balance and urea N kinetics were measured during the last 3 d of the period. Animals were then slaughtered and mucosa samples from the rumen, duodenum, ileum, and cecum, as well as kidney medulla and liver, were collected. Increasing N intake tended to increase N balance quadratically (1.5, 5.1, and 4.4 ± 0.86 g of N/d, P < 0.09), and linearly increased urinary N excretion (2.4, 10, and 16.5 ± 0.86 g N/d, P < 0.001) and plasma urea N concentration (4.3, 20.3, and 28.4 ± 2.62 mg of urea N/dL, P < 0.001), but did not affect fecal N excretion (5.0 ± 0.5 g of N/d; P < 0.94). Urea N production (2.4, 11.8, and 19.2 ± 0.83 g of N/d; P < 0.001) and urinary urea N excretion (0.7, 7.0, and 13.4 ± 0.73 g N/d; P < 0.001) increased linearly with N intake, as well as with the urea N recycled to the gastrointestinal tract (1.8, 4.8, and 5.8 ± 0.40 g of N/d, P < 0.001). No changes due to N intake were observed for creatinine excretion (518 ± 82.4 mg/d; P < 0.69) and clearance (46 ± 10.7 mL/min; P < 0.56), but urea N clearance increased linearly with N intake (14.9, 24.4, and 34.9 ± 5.9 mL/min; P < 0.04). Urea N reabsorption by the kidney tended to decrease (66.3, 38.5, 29.1 ± 12.6%; P < 0.06) with increasing N content of the diet. Increasing the level of N intake increased linearly the weight of the liver as a proportion of BW (1.73, 1.88, and 2.22 ± 0.15%, P < 0.03) but only tended to increase the weight of the kidneys (0.36, 0.37, and 0.50 ± 0.05%, P < 0.08). Urea transporter B was present in all the tissues analyzed, but UT-A was detected only in kidney medulla, liver, and duodenum. Among animals on the three diets, no differences (P > 0.10) in UT abundance, quantified by densitometry, were found. Ruminal-wall urease activity decreased linearly (P < 0.02) with increasing level of N intake. Urease activity in duodenal, ileal, and cecal mucosa did not differ from zero (P > 0.10) in lambs on the high-protein diet. In the present experiment, urea transporter abundance in the kidney medulla and the gastrointestinal tract did not reflect the increase in urea-N reabsorption by the kidney and transferred into the gut.